This prospective observational study aims to evaluate the relationship between changes in respiratory mechanics and cerebral oxygenation in adult patients undergoing elective lumbar disc surgery in the prone position under general anesthesia.
Cerebral regional oxygen saturation will be monitored using bilateral frontal near-infrared spectroscopy (NIRS), while respiratory parameters including tidal volume, respiratory rate, peak airway pressure, plateau pressure, positive end-expiratory pressure, and dynamic compliance will be recorded from the anesthesia ventilator. Measurements will be obtained at predefined time points before and after positioning the patient prone and after returning to the supine position at the end of surgery.
No changes will be made to anesthesia, ventilation, medication doses, or surgical management for research purposes. All clinical care will be provided according to routine practice by the responsible anesthesia team. The study will investigate whether changes in respiratory mechanics during prone positioning are associated with changes in cerebral regional oxygen saturation.
Age 18-75 years
Written informed consent
Scheduled for elective lumbar disc herniation surgery
ASA physical status I-III
History of increased intracranial pressure
Conditions preventing placement of cerebral NIRS probes
Development of severe intraoperative complications
Significant hemodynamic instability
Adult patients aged 18-75 years undergoing elective lumbar disc herniation surgery in the prone position under general anesthesia at Sancaktepe Şehit Prof. Dr. İlhan Varank Training and Research Hospital.
Cohort
Prospective
Prone Positioning
Procedure/SurgeryPatients will be placed in the prone position as part of routine surgical care for lumbar disc surgery. The study will observe changes in respiratory mechanics and cerebral regional oxygen saturation before and after prone positioning. No positioning intervention will be assigned or modified for research purposes.
Change in Cerebral Regional Oxygen Saturation (rSO2) During Prone Positioning
Bilateral frontal cerebral regional oxygen saturation (rSO2) will be measured using near-infrared spectroscopy (NIRS). Measurements will be recorded at baseline in the supine position (T0), 15 minutes (T1), 30 minutes (T2), 45 minutes (T3), and 60 minutes (T4) after prone positioning, and after return to the supine position at the end of surgery (T5).
Change in Dynamic Lung Compliance (Cdyn) During Prone Positioning
Dynamic lung compliance (Cdyn) will be recorded from the anesthesia ventilator at predefined intraoperative time points: baseline in the supine position (T0), 15 minutes (T1), 30 minutes (T2), 45 minutes (T3), and 60 minutes (T4) after prone positioning, and after return to the supine position at the end of surgery (T5)
Change in Peak Airway Pressure (Ppeak) During Prone Positioning
Peak airway pressure (Ppeak) will be recorded from the anesthesia ventilator at T0, T1, T2, T3, T4, and T5 to evaluate changes associated with prone positioning.
Change in Plateau Pressure (Pplat) During Prone Positioning
Plateau pressure (Pplat) will be recorded from the anesthesia ventilator at T0, T1, T2, T3, T4, and T5 to evaluate changes during prone positioning.
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